feat(graph): Implement PostgresSaver checkpointer integration

tests/graph/test_checkpoint.py

@@ -0,0 +1,49 @@
+import pytest
+from unittest.mock import AsyncMock, MagicMock
+from ea_chatbot.graph.checkpoint import get_checkpointer
+
+@pytest.mark.asyncio
+async def test_get_checkpointer_initialization():
+    """Test that the checkpointer setup is called."""
+    mock_conn = AsyncMock()
+    mock_pool = MagicMock() # Changed from AsyncMock to MagicMock
+    mock_pool.closed = True
+    mock_pool.open = AsyncMock() # Ensure open is awaitable
+    
+    # Setup mock_pool.connection() to return an async context manager
+    mock_cm = MagicMock()
+    mock_cm.__aenter__ = AsyncMock(return_value=mock_conn)
+    mock_cm.__aexit__ = AsyncMock(return_value=None)
+    mock_pool.connection.return_value = mock_cm
+    
+    # We need to patch the get_pool function and AsyncPostgresSaver in the module
+    with MagicMock() as mock_get_pool, \
+         MagicMock() as mock_saver_class:
+        import ea_chatbot.graph.checkpoint as checkpoint
+        mock_get_pool.return_value = mock_pool
+        
+        # Mock AsyncPostgresSaver class
+        mock_saver_instance = AsyncMock()
+        mock_saver_class.return_value = mock_saver_instance
+        
+        original_get_pool = checkpoint.get_pool
+        checkpoint.get_pool = mock_get_pool
+        
+        # Patch AsyncPostgresSaver where it's imported in checkpoint.py
+        import langgraph.checkpoint.postgres.aio as pg_aio
+        original_saver = checkpoint.AsyncPostgresSaver
+        checkpoint.AsyncPostgresSaver = mock_saver_class
+        
+        try:
+            async with get_checkpointer() as checkpointer:
+                assert checkpointer == mock_saver_instance
+                # Verify setup was called
+                mock_saver_instance.setup.assert_called_once()
+            
+            # Verify pool was opened
+            mock_pool.open.assert_called_once()
+            # Verify connection was requested
+            mock_pool.connection.assert_called_once()
+        finally:
+            checkpoint.get_pool = original_get_pool
+            checkpoint.AsyncPostgresSaver = original_saver